Placer gold mining device



June 11, 1940.

Filed June 9, 1938 w. w. GRAY 2,204,489

PLACER GOLD MINING DEVICE 2 Sheets-Sheet 1 INVENTOR 'WZWLAYQ ATTORNEYSJune 1 l, 1940. w. WLGRAY 2,204,489

PLACER GOLD MINING DEVICE Filed June 9, 1938 2 Sheets-Sheet INVENTOR 42Zfid-hmzf I ay mi 9 TTORNEYS a streamor other available supply of waterthe.

Patented June 11,1940

UNITED STATES PLACER GOLD MINING DEVICE William W.'Gray, Colorado spris, c010. App'lication June 9, 1938, Serial No. 21-25766 ,9 Claims. (01.209-419) This invention relates to mining and more particularly to aprocess and-apparatus for the dryplacer mining of gold and other values.

In the placer mining of gold an'd the like the 'values are found inmechanical mixture with rocks,'gravel, sand and other undesiredmaterials,

andsince the values form a relatively small-proportion of the mixture itis necessary for economical reasons to effect a substantial separationof the values from the other material-at'substantially the place wherethe placer'deposit: is found. 'When the placer deposit is located withinor near Water may be used to assist in'the separation of the values fromthe waste material, suchas in "the panning process of the prospector,and -several types of fairly successful apparatus have been developedfor this purpose. In other sections of the country, however, inwhich-substantial placer deposits of gold and the like-are found inlocations, there is no available water supply. Thus in certainmountainous sections of the Rocky 'Mountains gold in the former nuggetsf various sizes is foundin mixture with'rock, shale, gravel and the likein localitieswhere there is either no-water nearby or that which isnearby is not available for mining use. "So also-in certain sections ofthe desert, gold,generally in the form of fine grains or flakes andof asize substantially smaller than the nuggets found in mountainousregions, is-found in mixture with the sand and other deposits of thedesert. -Whi-le-the-process and apparatus of the present invention areadapted to be successfully used in the:mining and. separation of valuesin the presence of water,

it is of particular utility in the field of dry placer mining where'theplacer deposits occur in locali- 'ties which are often relativelyinaccessible and in which there is no available-supply of water.

It is, accordingly, aprimaryv object of the invention to provide asimple and inexpensive procr -ess-adapted to be used in the dryplacermining of gold and other values and providing for :the

separation of values in a dry or substantiallysdryv a state.

A further object is the provision lofxa .process in which placerdepositsofgold or other values having different sizes ranging from afine "grain or fiake to a relatively large-nuggetare separated from asubstantial portionjof the rock,. ;grave1, sandand. the like with whichit is mixedfor the economical transportation thereof or other .use toform a greatly enriched, or concentratedproduct, and in which no water.or.other.liquid,is, re- ,q'uiredto efiectsuch separation.

further obiect'isthe provision of-a dry placer mining process whichrequires no waterv or other 1 liquid and-which provides for, thecontinuous discharge of theseparate'd values and the "tailingsinto-separate receptacles orthe'like. 5 Astill further'objectisthprovision of simple andQinexpensiveapparatus adapted to carry out.the process of the invention. 'Other objects and-advantages will beapparent "from the following description, the appended 10 claims, 1 andthe accompanying drawings, in which:

v Fi'gflis' a schematic illustration of apparatus adapted to carryoutthe entire process of themvention; v

Fig." 21s a perspective view, partly broken'away, of a :riffleand-shaker feed plate constructeddn accordance withthe' invention: andadapted' to :be

'Fig'x3 is anenlarged section taken substantiallyi20 walongthe line:3-;3 of Fig. 2 andshowing the constructioniof the time in. greater"detail;

1 In -accordance iwith the invention the mixture l-of*valuesj-and'zwaste' material which comprises '..:rock,.:gravel,-' sandanditheli'ke is fiIStfdlViddelZf; .r acco'r'ding to: sizeintoa'plurality of: fractions or Hgradesin each of-which' thevalues andthe waste -ma-terial:are sofsubstantiallyzthe same. size. For

l this purpose. the mixture as it comes from-the placer depositmaybe-successivelypassed through-n -.a'plur.alityof screens'having'difierent sizedopeningsftherein' to cause the-mixture. to be separatedinto a plurality of graded or classified'fractions c in each'of'whichthesize'of the 'values is substantiallythe same. asJthe'size of the wastemateriallt35 :Eachof these fractions is then separatelyied toathe upperend of an inclined reciprocating vs'sh'aker plate which-causes, theclassified mixture 10f values andzwaste material tospread out across thesurface: of the plate-and flow downwardly in a relatively thin *streamatthe lower side of the :.plate.' 'fl heishakerxaplateicontinuously feedsthe relatively thinistream,of values andwaste mate-- rial'tosa'ninclined; rifile surface which comprises the topsofaplurality ofrelatively stiff elongateds bristles, preferably of metal wire, whichare;sup-

.. ported .in a substantially upright position andhavespacesbetweenupper ends of the bristles of ;-,,asizesubstantiallythesame as and coordinated with.,tlr e .size :ofthe values andthe.waste' mate-.5

,rial fed thereto. The rifflelis vibrated or reciprocatedsin a.:direction substantially transverse to pthe movement of materialthereover and this reciprocation together: withv the inclination ofthe,.-riifle causes thesmixture ofvaluiasand waste Inaterial to move overthe top of the riflie in a relatively thin stream. The stream of valuesand waste material which is fed to the rilfle by the shaker plate andpasses thereover preferably comprises a single layer of the sizedmaterial as distinguished from a deep bed of the product. Theinclination of the shaker feed plate and the inclination of the rifilesurface may be separately adjusted to provide the desired thinness inthe stream of material fed to the rifile and to effect the continuouspassage of material over the bristle surface in a substantially uniformthin layer.

The vibration of the riflie causes the values which are of relativelyheavy specific gravity compared to the waste material mixed therewith towork their way downwardly into and through the spaces between thebristles, while the relatively lighter waste material is maintained ontop of the bristles and passes downwardly over the surface formed by thetops of the bristles. Openings are provided in the riflle at the lowerend of the bristles to provide for the continuous discharge ofthe valuesinto a suitable receptacle or the like. The tailings of waste materialwhich have passed downwardly over the top of the bristle surface aredischarged at the remote end of the riflie into a suitable trough or thelike for disposal as desired.

In the preferred form of the invention the mixture of values and wastematerials from the placer deposit are continuously fed to the screensand the classified fractions of values and waste material arecontinuously fed to a plurality of separate reciprocating shaker plateswhich continuously feed the segregated fractions to a plurality ofseparate rifiies of the character described. In this manner each of thesized fractions is simultaneously processed to separate the values froma substantial portion of the waste material and the values and tailingsfrom each fraction are continuously discharged into their respectivereceptacles or the like. The number of screen'sections and the size ofthe openings therein will depend upon the size of the'gold or the likecontained in the placer mixture, the important feature of this portionof the process being to obtain classified fractions of themixture inwhich the values and the waste mateseparation into a sized fraction andthe tailings may be found satisfactory. It will be evident from theforegoing that only such screened fractions as contain an economicalquantity of gold will be passed to a shaker plate and riflie. Where,

- however, the deposit contains or may contain 1 values of larger sizesthe tailings from the screening operation may be also fed to a shakerplate and rifl'le. 1

The process as thus described requires no water or other liquid and isaccordingly particularly adapted for use in dry placer mining and inlocalities where water is not available for mining use. The apparatusrequired to carry out the process is simple, inexpensive, and may bemade in relatively small sections of light weight which can be readilytransported by pack or hand to relatively inaccessible places. The

,means of baiiles 20, 2I

. those in section I9 of an even larger size.

. feed plate.

seen that the trough 21 is provided with an openprocess effects asubstantial separation between the values and the waste materialproviding a greatly enriched product as compared with the originaldeposit, and thus provides for a dry placer mining operation in whichthe values may be economically transported over a relatively longdistance for further purification and for the ultimate recovery of thepure gold.

Referring to the drawings which illustrate a preferred embodiment ofapparatus adapted to carry out the. process and in which like referencenumerals designate like parts in the several views, there is shown acylindrical screening device In which is inclined to the horizontal andis provided at its upper end with an opening II adapted to receive thedischarge end of a hopper I2. The screening device I0 is supported forrotation about its axis by any suitable means (not shown) and isillustrated as being provided with an annular gear I3 adapted to meshwith a pinion, I4 carried by a shaft I5. The

shaft. I5 is rotated by any suitable means to effect rotation of thecylindrical screening device about its axis.

The screening device I6 is divided into a plurality ofv screeningsections I6, II, I8 and I9 respectively which are preferably separatedby and 22. Each of the screening sections is provided with a pluralityof screening apertures 23 which are of a different size in each of thesections. In the type of screening device illustrated in the drawings,the apertures 23 in the screening section I6 will be relatively small,those in the section II somewhat larger, those in section It stilllarger and Thus as anexample the screening apertures in the uppersection I6 may be approximately the size of a pinhead while those in thelowermost section may have a diameter of A of an inch or more. It willbe evident from the foregoing description of the process, however, thatthese sizes are merely illustrative, and that the actual sizes of thescreening apertures as well as the number of screening sections willdepend upon the size of the values which are found in the placer depositwith which the apparatus is to be used. The screen device is providedwith an opening 24 at its lower end for the discharge of the particlesof values and waste material which are too large to pass through theapertures in the last screening section.

Hoppers 25 catch the sized material as it passes through the variousscreen sections and discharge it into ducts 26 which convey it to atrough 21 provided on a shaker feed plate 28. Each of the screeningsections is provided with a separate hopper which continuously feeds thesized material through the ducts 28 to a separate shaker Referring toFigs. 1 and 2 it will be ing 29 which permits the sized mixture ofvalues and waste material to pass onto the shaker feed plate 28. Theshaker plate is inclined downwardly from the trough 2? and is adjustablysup: ported by-any suitable means such as the guide bar 30 and one sidewall 3| of the rifile 32 and is adapted to be laterally reciprocated tocause the material fed thereto to spread out over the surface of theplate and work downwardly in a relatively thin stream, preferablycomprising at the lower end a single layer of sized material. Suitablemeans (not shown) may be provided for adjusting the tilt or inclinationof the shaker feed plate to provide the desired thinness of emer ereedat the lower side. *Side members 33 pr vent the material from spillingover the sides of the shaker plate. p

The shaker-plate continuously feeds the thin ported substantiallyupright in the rifile with spaces therebetween at the upper ends of sub-;stantially the same size as the size of the-values and-waste materialwhich are fed to the ri-filebytheshaker plate 28. Thus in the-rifile'32'whlch is connectedto the finescreening section l6 the upperendsofthe bristles are relativelycl'ose to- -gether as-indicated at 35a inFig. l to provide spaces between 'the bristles which correspond in'sizeto the apertures 2! in the screeningsec- 'tionJB. The bristlesintheriflle connected *to thescreening section -l1 are spacedfarther apartat-the upper ends as 'indicated -at 35b-in Fig- 1 to -provide openingscorresponding with'the open ings in this screening section. Theriflleswhich receive the sized material from the screening sections 1 i8and'l'Q have openings "between upper ends of the bristles which-arespaced correspondingly farther apart, respectively, as indicated'at 350and 35d in'Fig-s: 1, to provide spaces therebetween corresponding to thesize of the material fed thereto "through the openings'in these-screening sections. in 'tufts as s'ho'wn in Figs. l and 3, and in the'lrifiles adapted to receive thefiner material the ?upper ends-of theindividual bristles are spread apartto provide the desire'dspacing-therebetween.

as indicated at (remand 35b in Fig. 1, whereas in rifiies adapted toreceive coarser -material the :being shorter and finer "than thebristles 35c and 35d. The length and fineness of thebr'istles may bevaried and graduated as desired oras may be found necessary tofeffectthe continuous separation and discharge of values-and wastema- Referringto Figs. 2 and 3, the riffieis'shown -as comprising side Walls 3| andend walls 36. 'Metallic plates 37 are attached to the end, walls 36 andcarry aplurality of transversely extending tuft-supporting bars 38.

means such as bolts39. The bars 38 are preferably constructed from sheetmetal and are substantially V-shaped in transverse cross-section asshown in Fig. 3. .The V-shaped bars-are attached to the metallic plates31 by anysuitable means :such as'soldering, welding and the like andaresupported' in the riffle with the apex portions thereof towards thetop of the rifile,

7 'shown) forj-adjusting'the tilt of the rifile. The bristles aresupported The plates 31. are attached to the. end walls by any-suitable3 "Spaced rein-forcing rods- 48 extend -'betweenfthe side *walls 3 l ofthe -riffle beneath the inverted v sha'ped ba'rs tfl andserve to supportthe latter. *The bars 38 are preferablysoldered or otherwiseattach'ed'to the rods-4| to provide a rigid Structure. The rods ll' arepreferably round as-illustrated to prevent the accumulation of. valuesthereon. The riffle isdncli-ned to the-horizontal topro- 'vide adownwardly *slcnping surface over which 10 the materialfe'd to the topsof the bristles passes. This surface which is defined by the bristletops -mayh-ave the same inclination as the shaker -feed plate whichfeeds the material to theriffie eorit may have a greater orless'inclination' as found 'necessary in-the operation of the device. II-h Fig. l the 'rifile surface 35b isillustrated- 'as 'having a greaterincline thanthe shaker feed -plate"28 and the surface 35a is illustratedashavmg astill greater incline. In practice the inclination oftheriffle" surface will be adjusted-[to #provide the' desiredcontinuousfiow'or movement of material in a relatively thin stream, preferablycomprising a'single layer of the material, over the to'ps of thebristles and to effectseparation of the values in the-spaces between thebristles. The riflie issupported in the inclinedposition byan'ysu'itable means such as the guide bars 42 which extend across the rifilebeneath the side members 1 '3l and are provided with suitable means (notIn order to cause the waste material to pass continuously downwardlyover the tops of the bristles'and' to effect separation of the valuestherefromby causing the heavier Values to passdown- 3 'war-dly throughthe spaces between the bristles, the riille. is reciprocated or vibratedon the guide bars42 by'a suitable'means such'as the eccentric *45*and.'pitman"46; "This reciprocation is'in a direction substantiallytransverse to the move- 40 ment -of imaterial over the tops of thebristles. The shaker feedplate28 maybe'reciprocated by the sameeccentric which reciprocates the rifiie I andfor' thislpurpose isshownas b eing supported atlthe' lower side by "one of the side members 3| of'45 the riffie, as'hereinabove described, and as hav-- :ing its end'wallsj33 engaged between the end walls -36'of'the rifile. Hi-ngemeans-3|" or the like may be provided to secure the shaker feed plate to'the, riffle 'and at the same time permit separate adju'stme'ntbftheinclination of the plate and riifle; The side members-3| of the riflleterminate :slightly below'the' plane or surface definedby the tops ofthe bristles'whilethe end walls 36 extend -upwardly a considerabledistance above this plane 65 to keep thematerial passing over thebristle surface fromspilling over theends of the rifile. In 7 arillleadapted .to be supported at considerable inclination in use thebristles may be supported a so as to slope towards the upper sidemember-31 0f the riflle *so that in the use of the device the bristleswill stand substantially vertical with their tops defininga downwardlysloping surface over which the material passes, thereby facilitating ithe trapping of thevalues and the downward passageof the values inthespaces between the bristles'fordischarge at the lower ends thereof.This sloping of the bristles may be readily accomplished 'bymountingtheinverted V-shaped bristle swpporting bars 38 atthe desiredangles to theverticaland with the apexes thereof directed generally towardsthe upperside member 31.

To provide'for the continuous discharge of the values'separatedfrom'the' waste material the bars between through which the values maypass to be received within a hopper of a suitable receptacle 52. Thesloping sides of the triangular shaped bristle supporting bars 38provide troughlike channels for directing the values towards theopenings 50 between the bars. The tailings of waste material arecontinuously discharged from the lower side of the riille which isremote from the shaker feed plate and pass over the side member 3| intoa hopper 53 or the like to be disposed of as desired.

The operation of the apparatuswill be apparent from the foregoingdescription. The screen member I E] is rotated by means of the shaft I5and pinion i l and a mixture of values and waste material directly fromthe placer deposit is continuously fed into the upper end of the screenmember by means of the hopper l2. Owing to the inclination of the screenmember the material fed thereto gradually works towards the lower endand during such travel is continuously agitated and tumbled by means ofthe rotation of the screening member. A mixture of values and wastematerials sufficiently small to pass through the apertures of the firstscreening section IE will be separated and this sized or classifiedfraction is passed to the first shaker plate 28 by means of the hopper25 and duct 26. The material which is too large to pass through theapertures of the first screening section travels downwardly into thesecond screening section I] where a fraction of larger sized values andwaste material is separated and fed onto a second shaker feed plate. Theremaining material feeds downwardly into the third screening section l8where a fraction of still larger size is separated and fed to a thirdshaker feed plate. The remaining material passes into the lowerscreening section 28 where a fourth and larger sized fraction isseparated and fed to the shaker feed plate of a fourth rifiie. Thetailings which remain are discharged through the opening 22 in the lowerend of the screening member, and in the embodiment of the inventionillustrated are received by a hopper 25 which feeds the tailings fromwhich substantially all the values have been removed to a duct 26' fordisposal as desired. The vibration of each of the inclined shaker feedplates causes the fraction of values and waste material fed thereto tospread out over the relatively wide surface of the plate andworkgradually downwardly towards the lower side thereof where itcontinuously feeds in a relatively thin stream to the surface formed bythe upper ends of the rifile bristles. As hereinabove pointed out it ispreferable that the stream of material as fed onto the bristles from theshaker feed plate have a thickness corresponding to substantially asingle layer of the sized material.

The inclination of the rifiie together with the transverse vibratorymovement thereof causes the material fed to the rifile to pass over thesurface formed by the tops of the bristles and work downwardly towardthe lower side thereof. During this travel the heavier values work theirway into and through the spaces between the bristles and are thusseparated from. a substantial portion of the waste material which is oflighter weight and is retained on the tops of the bristles to pass overthe bristle surface and be discharged at the lower side thereof. Thevibratory movement of the bristles also causes the values which havebeen trapped within the spaces to work downwardly therebetween and becontinuously best shown in Fig. 3 to provide openings 50 theredischargedfrom the riflie by means of: the openings 50 provided therein at thelower ends of the bristles. The discharged values are received in asuitable receptacle and may be further processed on the spot to furtherpurify them or may be economically transferred over even a relativelylong distance for such processing. Thus a placer deposit containing arelatively small proportion of gold particles therein may be soconcentrated by the process and apparatus of the present invention thatthe concentration of gold to sand, gravel and the like may be soincreased as to make it commercially practicable to transport thetreated product to a point where the final recovery of the pure gold canbe eifected.

While the method herein described, and the form of, apparatus forcarrying this method into effect, constitute preferred embodiments ofthe invention, it is to be understood that the invention is not limitedto this precise method and form of apparatus, and that changes may bemade in either without departing from the scope of the invention whichis defined in the appended claims.

What is claimed is:

1. An apparatus of the character described for the mining ofsubstantially dry placer deposits of gold and the like, comprising meansfor continuously feeding a mixed fraction of values and waste materialhaving the values and the waste materials of substantially the same sizein a relatively thin stream, a riffie surface for receiving saidfraction, said surface comprising the upper ends of a plurality ofrelatively stiff, elongated bristles maintained substantially uprightand having spaces between bristles of a size coordinating with the sizeof the material received on said surface and adapted to permit values ofrelatively heavy specific gravity to pass downwardly therebetween whilemaintaining waste material of relatively lighter specific gravity on thetops thereof, means for reciprocating said rifi'le surface to cause saidthin stream of values and waste material to pass over the tops of saidbristles and to effect selective separation of values within said spacesbetween the bristles, means for continuously discharging values from thelower ends of said bristles, and means for continuously dischargingtailings of waste material from a side of said bristle surface.

2. An apparatus of the character described for the mining ofsubstantially dry placer deposits of gold and the like comprising meansfor feeding a mixed fraction of values and waste materials having thevalues and waste materials of substantially the same size in asubstantially dry state and in a relatively thin stream to the upperside of a downwardly sloping rifile surface, said surface comprising theupper ends of a plurality of relatively stiff, elongated bristlesmaintained substantially upright and having spaces between the bristlesof a size substantially the same as the size of the values and wastematerial fed thereto, means for reciprocating said rifile surface tocause said thin stream of values and waste material to pass downwardlyover the tops of said bristles and to effect selective separation ofvalues within said spaces between the bristles, means for continuouslydischarging values from the lower ends of said bristles, and means forcontinuously discharging tailings of waste material from the lower sideof said rifile surface.

3. An apparatus of the character described for the mining ofsubstantially dry placer deposits of gold and the like comprisingmeansfor feeding a aaoaase:

a mixed: fraction; of: values -andt'wasteimaterial.

thetops "of a. plurality r of relatively stiff} 'elon:-

gated bristles maintained. substantially uprightand having spacesbetweenzbristlesrof a'sizezsub.r stantiallyithe same as thersizeof:the=valueslandE waste material fed thereto, meansforlrecip'rocat-i ingsaid riflle'andxshak'er plate means in-a -direction substantiallytransverse to the movement of material thereon to cause the material tofeed downwardly over the topsjjof said bristles and to effect selectiveseparation and downward move ment of values within said spaces between'the 1 bristles, said rifile having a plurality of openings in'thebottom thereof adjacent the lower ends of said bristles to provide forcontinuously discharging values; and means for continuouslydischargingtailings of waste material from the lower side of saidbristle surface. f

4. In an apparatus of the character described for utilization in themining of substantially dry placer depositsof gold or thelike andadapted to provide for the separation of values from waste materialwithout the addition of water or other liquid, a rifile comprising sideand end walls, a

' plurality of stiff, elongated wire bristles supported substantiallyupright within said side and end walls to provide aibrush-like rifllesurface at the upper ends of the bristles adapted to receive a mixtureof values and waste materials of *apredetermined size,- said rifilesurface lying in a plane which is raised slightly above the tops of saidside walls, means for supporting said bristles at the lowerends'thereof, said bristles being arranged with spaces therebetweenwhich define value segregating openings of a predetermined substantiallyuniform size in said brush-like riflie surface and which provide for thedownward passage of the separated values within said spaces, the size ofsaid value segregating openings in the rifiie surface being coordinatedto the predetermaterial without the addition of water. or other.

liquid, a rude comprising side and end walls, a

plurality of substantially V-shaped bars extending between said endwalls and arranged with their apex towards the top of said riffle, saidbars being spaced apart to provide openings therebetween, each ofsaidba'rs having a plurality of spaced apertures therein at the apexportion thereof, a plurality of stiff elongated bristles are ranged intufts and having the lower endsthereof passing through said aperturesand received withinthe V-shaped portion of said bars, means within. saidV-shaped portion of the bars for securing the lower ends of saidbristles therein, said bristles extending;substantially.:uprightand-pro, vidingarat;thesupperj'ends a: brush like rifile" surface:adaptedcto; receive -armiz'rture of values and waste' materials ofazpredetermined size, saidbris-v tles: being arrangedwithikspacestherebetween' which define value segregatingzopenings of apredetermined, substantially uniformv size; in. said brushd-ike rilflesurfaceand which-provide for the downward passage. of the separatedvalues witha in said spaces; the size of said valuesegregating openingsin the riffle surface beingzycoordinatedi to; the predetermined size ofthe material adapted 'toJbe received on" said surface toeffectselectiver: separation; of values: within: said "openings;

saidzriillasurface-lyingpin a3 plane which is raised-.-

above: :the tOIJSiOf'jSitid sidewalls; and: saidend walls being:provided with; extensions rising above theriiilesurfa'ceiformedaby the;tops;,-of;-said*brise tles. i Y

6. In an apparatus of the character described for utilization in'the'mining of substantially dry placer deposits of gold or the like andadapted to provide for the separation of values from'waste materialwithout the addition of water or other liquid, a riifle comprising aframe," a plurality of relatively stiff elongated bristles arranged intufts and mounted substantially upright in said frame with the upperends of thebristles providing a substantially flat resilient surface,means for supporting said-tufts at the lower ends of said bristles withpredetermined spacings between the tufts, said'supporting meansproviding a plurality of openings in the bottom of said frame in directcommunication. with said spacings between; said tufts, andsaid spacingsbetween thetufts providing a pluralityof openings of predetermined sizein said resilient surface.

'7. In an apparatus of the ,character'described for utilization in themining of;- substantially dry placer deposits of gold or the like .andadapted to provide for the separation of'values from waste materialwithout the addition of water or other liquid, a riflle comprising aframe, a plurality of relatively stiff elongated wire bristlesarrangedin tufts and mounted substantially upright in said frame with the upperends of the bristles providing a substantially fiat resilient surfaceadapted to receive a fraction of values and'waste material thereon,means for supporting said tufts at the lower ends of said bristles withpredetermined spacings between the tufts, said supporting meansproviding a plurality of openings in the bottom of said-frame in directcommunication with, said spacings between said tufts, and said 7spacings, between the tufts providing a plurality of openings ofpredetermined. size in said resilient surface, the size of said openingsand the stiffness of said bristles being coordinated to the size of thework material adapted to be received on said resilientsurface to providefor yieldingly receiving values of relatively heavy specific gravitywithin said openings while maintaining waste material of lighterspecific gravity upon the'itop of said surface. 8. In an apparatus ofthecharacter described for utilization in the mining of substantiallydry placer deposits of gold or thelike and adapted to provide fortheseparation of values'from waste material without the addition of wateror other Waste material thereon, means for supporting.

said resilient members in said frame to provide a plurality of openingsof, predetermined sizev in said surface adapted to yieldingly receivevalues therein, said suporting means providing a plurality of openingsat the bottom of said frame communicating with said openings in saidsurface and providing for discharge of values from said riflle, and saidresilient members having an inherent stifiness sufficient to maintainwaste material of relatively light specific gravity upon the top of saidsurface while providing for yieldably receiving values of greaterspecific gravity within said openings.

9. A value concentrating apparatus of the character described comprisingmeans for feeding a mixture of values and waste material in a rela-,tively thin stream, riflle means for receiving said mixture, said rifilemeans comprising a plurality of relatively stifi resilient membersarranged to provide a substantially fiat surface having a plurality ofyieldable openings of predetermined size therein, the size of saidopenings and the stiffness of said resilient members being coordinatedwith the size of the work material received on said riffle means toprovide for yieldingly receiv-, ing value of relatively heavy specificgravity within said openings while maintaining waste material of lighterspecific gravity upon the top of said surface, means for vibrating saidriflie means charging values from the bottom of said rifile means, andmeans for continuously discharging 15 tailings of waste material fromsaid surface of the rifile means.

WILLIAM W. GRAY.

